Department of Computer Science | Institute of Theoretical Computer Science | CADMO

Theory of Combinatorial Algorithms

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar (in cooperation with M. Ghaffari, A. Steger and B. Sudakov)

Mittagsseminar Talk Information

Date and Time: Tuesday, December 15, 2015, 12:15 pm

Duration: 30 minutes

Location: CAB G51

Speaker: Emo Welzl

Embracing Triangles and Simplices

A triple of points in the plane forms an embracing triangle if the origin lies in its convex hull; correspondingly, d+1 points in d-space form an embracing simplex if their convex hull contains the origin. Via Gale duality, the set of embracing simplices of a set S of points is in correspondence to the facets of some simplicial polytope, assuming that S forms with the origin a set in general position.
We discuss the complexity of counting the number of embracing simplices in a set S, starting with a simple formula for embracing triangles. As a by-product we can count the number of facets of the convex hull of n points in general position in d-space orders of magnitude faster than the number of these facets, provided n-d is constant. (Joint work with Alexander Pilz and Manuel Wettstein)


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